Effect of double bond geometry in sphingosine base on the antioxidant function of sphingomyelin.
We previously showed that sphingomyelin (SM) inhibits peroxidation of phosphatidylcholine (PC) and cholesterol. Since SM uniquely has a trans unsaturation in its sphingosine base, we investigated whether this feature is important for its antioxidant function. Substitution of the natural trans Delta(4)-double bond with a cis double bond (cis-SM), however, increased SM's ability to inhibit Cu(2+)-mediated 16:0-18:2 PC oxidation by up to eightfold. Dihydro-SM, which lacks the double bond, was equally effective as trans-SM. In contrast to its effect in the sphingosine base, the presence of a cis double bond in the N-acyl group of trans-SM was not protective. cis-SM also inhibited the oxidation of cholesterol by FeSO_(4)/ascorbate more efficiently than the trans isomer. The enhanced protective effect of cis-SM is selective for metal ion-promoted oxidation, and appears to arise from a decrease in the effective concentration of metal ions. These studies show that the trans double bond of SM is not essential for its antioxidant effects.
Subbaiah
Papasani V
PV
Department of Medicine, Section of Endocrinology and Metabolism, University of Illinois at Chicago, 1819 West Polk Street, Chicago, IL 60612, USA. psubbaia@uic.edu
Sircar
Debajit
D
Lankalapalli
Ravi S
RS
Bittman
Robert
R
D000975:Antioxidants / Q000737:chemistry*; D001205:Ascorbic Acid / Q000737:chemistry; D002413:Cations, Divalent; D002784:Cholesterol / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D015227:Lipid Peroxidation; D010084:Oxidation-Reduction; D010713:Phosphatidylcholines / Q000737:chemistry; D013109:Sphingomyelins / Q000737:chemistry*; D013110:Sphingosine / Q000737:chemistry*; D013237:Stereoisomerism
D000975:Antioxidants; D002413:Cations, Divalent; D005296:Ferrous Compounds; D010713:Phosphatidylcholines; D013109:Sphingomyelins; C020748:ferrous sulfate; D003300:Copper; D002784:Cholesterol; D013110:Sphingosine; D001205:Ascorbic Acid